The invention relates to a ground covering of pentagonal shaped concrete slabs which abut one another with joints and which each have two adjacent straight sides of equal length disposed at an obtuse angle, two further adjoining sides of equal length and a side disposed therebetween and having a greater length than the further sides of equal length, the slabs forming a group of three with star-shaped joints formed between the abutting further straight sides.
Various constructions are known of ground coverings consisting of polygonal shaped concrete slabs abutting one another with joints. As a rule the shaped slabs have a regular shape which enables the individual slabs to be laid against one another as desired. Such a ground covering often has to enable accumulating surface water to trickle through the joints into the subsoil. To facilitate the removal of surface water, the shaped blocks should not abut one another at their sides, but be places at a distance, with the formation of joints. One disadvantage of such shaped slabs is felt to be that they have a regular shape, as a result of which the appearance of a ground covering is boring by comparison with a ground covering produced from irregular quarry slabs.
In one prior art ground covering of pentagonal shaped concrete slabs abutting one another with joints (DE 0 94 04 146) all the sides are straight. A group of three identical shaped slabs is extended by a fourth identical shaped slab to give a group of four with six corners and an outer contour symmetrical with respect to axes placed perpendicularly on one another. A ground covering made up of such groups of four shaped slabs has a boring appearance in contrast with a ground covering produced from irregular quarry slabs.
It is an object of the invention to produce a ground covering of polygonal shaped concrete slabs which on the one hand can easily be laid but on the other hand has a lively appearance similar to that of irregular quarry slabs.
This problem is solved in a ground covering of the kind specified by the features that the further sides of equal length of each shaped slab have the same concave curvature and the longer side disposed therebetween opposite the straight sides has a convex curvature corresponding to the concave curvature and twice the length of the concave sides, the outer convex sides of one group of three abutting the concave sides of the adjacent groups of three and vice versa.
Although the shaped slabs of such a ground covering all have the same shape, something which simplifies their production and laying, the different shapes of lengths of the sides make the ground covering look completely irregular at first glance and give the covering an appearance similar to that of irregular quarry slabs.
A ground covering of such shaped slabs is also suitable for the effective drainage of surface water, more particularly if according to one feature of the invention the sides of each shaped slab bear over a proportion of their length and height cams acting as joint-forming spacers. In this construction of the invention each side does not need to have spacers; it is enough for one of the abutting sides of two shaped slabs to have a spacer. As regards production and laying, however, it is simpler for all the sides to have such spacers, which then co-operate in pairs. In any case the spacers ensure that a wide enough joint is obtained during laying.
The spacers, which are present only over a proportion of the height of the shaped slabs, should be completely absent in the upper zone, to form a continuous joint at that place.